In the figure, a parallel beam of white light is incident on the plane of slits S₁ and S₂. Find the distance of the nearest white spot on the screen from O. Assume D≫d and d≫λ.

Question

G1 Physics · Accepted Answer

For white light, all wavelengths are simultaneously bright only where the geometrical path difference is zero. From the slit geometry, the midpoint of S₁S₂ lies d/3 above O. The point on the screen opposite this midpoint has equal distances from S₁ and S₂, so it is the nearest white spot. Distance from O=d/3. Option B.